Research On Hydrological And Ecological Functions Of Forests In Jinyun Mountain, Chongqing

Based on the analysis of large amount of data, this thesis has studied the hydrological and ecological functions of several common forest types:coniferious-broad leaved mixed forest,broad leaved forest,Phyllostachys pupescens forest and evergreen broad-leaved shrubs. The emphasis of this study is hydrological and ecological characteristic of canopy layer,litter layer,soil layer, including infiltration,water holding characteristic of soil,surface and undersurface flow, in different typical forests. Furthermore,this study carried on analogy analysis of hydrological and ecological functions in various typical forests,with the help of regression analysis,correlation analysis grey relational analysis and other statistical methods. Finally,based on the comprehensive assessment of different indices in various typical forests,this study set up an assessment index system of forest hydrological and ecological functions for Jinyun Mountain region of Chongqing with the method of entropy weight coefficient method.Specific conclusions are as followings.1)The results showed that the priority of canopy interception capability of different vegetation types was mixed broadleaf-conifer forest (18.90%) >evergreen broad-leaf forest (11.806%) >Phyllostachys pubescens forest (10.68%).They are related to canopy interception capacity to precipitation quantity. For various types of forests,the amounts of precipitation in and out have obvious positive linear relations,with a relatively high correlation coefficient.What's more,the data from model and experiment have a high fitting degree. By analyzing and comparing the results,we concluded that the effect of Forest Canopy Interception of mixed forests was the most fine.2)The water retention rates in typical stands of various types of forest have an order as follows:evergreen broad-leaved shrubs>coniferous-broad leaved mixed forest>evergreen broad-leaved forest>Phyllostachys pupescens forest. The water retention rates of decomposed layer and semi- decomposed layer are higher than non- decomposed layer in all typical stands. The order of water retention depth is:evergreen broad-leaved shrubs>coniferous-broad leaved mixed forest>evergreen broad-leaved forest>Phyllostachys pupescens forest,and the largest one in evergreen broad-leaved shrubs is 8.06mm/h,the smallest in Phyllostachys pupescens forest 3.34mm/h.The maximum water retention is related with stand type,component structure,stand volume and the condition of decomposition. The maximum water retention ratio of litters in several typical forests around the three gorges reservoir is between 206.05 and 289.13 percent. Meanwhile the effective flood storage capacity is between 18.232 and 54.144 (t·hm-2),which is equivalent to 1.8～5.4mm in depth.,which order is evergreen broad-leaved shrubs(54.144 t·hm-2)>coniferous-broad leaved mixed fores(t37.987 t·hm-2)>evergreen broad-leaved forest (32.150t·hm-2)>Phyllostachys pupescens forest.(18.232 t·hm-2)。 3)The results of a study on the soil physical property and soil infiltration of different typical forest stands. The study showed that the effective water storage capacity of shrubberies which have good improvement on soil is much higher than others. The effective water storage of the soil was 1.4 times as high as that of arable P. pubescens forests soil, 2.14 times of farmland soil. In general, the soil of the evergreen broadleaved shrub forests has the best hydrological function in soil water retention capacity and infiltration property, which early infiltration rater was 10.169mm/min demonstrated strong permeability. These characteristics are better in the broad-leaved and needle leaf mixed forest than in the evergreen broadleaf forests, while the performance of the P. pubescens forests is the worst in both capacities. But for the short-duration high intensity rainfall, the P. pubescens forests is slightly better than the broad-leaved and needle leaf mixed forest and the evergreen broadleaf forests.4)Due to the monthly rainfall characteristics from 2002 to 2004, the order of surface runoff is obtained by comparative analysis which is: Phyllostachys pupescens forest> coniferous-broad leaved mixed forest> farmland> evergreen broad-leaved forest. According to the measured data from 14 rainstorms we know that Under the same storm condition, the surface runoff of evergreen broad-leaved forest and evergreen broad-leaved shrubs is the lowest, then coniferous-broad leaved mixed forest.And Phyllostachys pupescens forest is the highest. So for the same capacity of flood storage, the ability of Phyllostachys pupescens forest is the poorest. Evergreen broad-leaved forest and evergreen broad-leaved shrubs have the significantly functions to reduce the surface runoff .5)Based on the theory of grey correlation degree analysis, it is found that for various typical forest types and farmland, the closest factors related with runoff are precipitation and maximum rainfall intensity within 10 mins, and with little difference, both are main influence factors. Specifically, coniferous-broad leaved mixed forest,Phyllostachys pupescens forest and farmland relate with precipitation closest, while evergreen broad-leaved forest and evergreen broad-leaved shrubs with maximum rainfall intensity within 10 mins. Through regression analysis of SPSS13.0, the results of models show that for four types of forest stands and farmland, there is a cubic curve relation between runoff and precipitation, which accords with the fact relatively. The simulations have a fitting degree over 0.9. Correlation analysis between runoff coefficient and ground cover and physical properties of soil improved that all of the factors are positive correlation with the runoff coefficient,which order is the thickness of litter>coverage and height of shrub and grass>canopy density>initial infiltration rate>The maximum water retention percentage>effective soil water store capacity> non-capillary porosity.6)By comprehensive assessment of 15 indices which affect the functions of the eco- hydrological with the entropy weight method, the synthetic values are obtained as follows:Zi=( 0.2011,0.1704, 0.1418,0.4867). With the highest capacity of water resource conservation,the synthetic value of evergreen broad-leaved shrubs is highest, coniferous-broad leaved mixed forest and evergreen broad-leaved forest coming next, and Phyllostachys pupescens forest is relatively low.7)The Hydrological and Ecological Functions of forest in Jiyun Mountain were evaluated by using the methods of shadow price method,which is 6.82 million yuan.